Isatin derivative and process of making same



Patented Feb. 5, 1929.

UNITED STATES PATENT OFFICE.

MAXIMILIAN PAUL SCHMIDT, OF BIEBRICH-ON-THE-RHINE, AND OTTO HERRMANN, OF MAINZ, GERMANY, ASSIGNORS TO GRASSELLI .DYESTUFF CORPORATION, OF NEW YORK, N. Y. A CORPORATION OF DELAWARE.

ISATIN DERIVATIVE PROCESS OF MAKING SAME.

No Drawing. Application filed September 13, 1926,-Serial 110,135,280, and in Germany June 6, 1925.

Our present invention relates to new isatin derivatives and to a process of preparing the same.

For the preparation of indigoid dyestuffs containing the indol residue linked in alpha position, there were hitherto used isatin-alpha-chlorides or isatin-alpha-anilides causing them to react with a compoundcontaining a CH=C.CH- or CH,CO group. The condensation in question has, in most cases, to be efiected in presence of an organic solvent or condensing agent, such, for instance as acetic acid anhydride.

Now we have succeeded in preparing a new class of isatin derivatives which are soluble in water and which can be combined in an aqueous solution With a reactive ketomethylene compound, such as naphthol, oxythionaphthene, indoxyl, aoenaphthenone or the like, so as to give indigoid dyestuffs.

The said new condensable isatin compounds are produced for instance by the action of sulfites upon isatin-alpha-chlorides, their substitution products, homologues or analogues preferably the isatin-alpha-chloride is suspended in an aqueous solution of sodium sulfite of, for intsance, 10% strength and slowly heated to about 90 C. while stirring, the chloride gradually dissolves and the reaction product may be separated from the solution .by salting out with, for instance sodium chloride. They may also be obtained from the dehydroindigo bisulfites described by Kalb see Berichte der deutschen chemischen Gesellschaft vol. 42, page 3653 E). This author has already made the observation that the dehydroindigo bisulfites are very apt to decompose in al aline solution with separation of the corresponding indigo. He recovered for instance from dehydroindigo bisulfite by treating it with caustic soda solution in the cold, a quantity of indigo amounting to about half of that of the theory and moreover a colorless solution which chiefly contained anthranilic acid.

By our own researches we have now found that the decomposition of dehydroindigo bisulfite' and its derivatives may also be conducted in such a manner that besides the indlgo 1n question (i. e. half of the theory) the same cond'ensable isatin compounds'are obtained as are produced by the action of sulfites upon isatin-alpha chlorides. This result is obtained by treating the dehydroindigo bisulfite compounds'by means of weakly alkaline agents. For this purpose it is not necessary to isolate previously the dehydroindigo bisulfite compounds produced by reaction of dehydroindigo acetates with sulfites, but they may immediately be further decomposed in solution whereby it is possible to obtain the water-soluble isatin derivatives directly from' the dehydroindigo acetates.

The new compounds contain in the molecule two sulfur atoms to one nitrogen atom. Their structural formula could not as yet be defimtely determined probably they correspond to the general ormula:

wherein R maybe substituted. They readily crystallize in the form of radially arranged ye low needles. .They resist well the action of dilute acids even in the heat. They are decomposed by concentrated mineral acids and ,then chiefly form the corresponding in digo. They are also unstable in a stronger alkaline solution but are not transformed into indigo as is the case with the dehydroin- The-following examples illustrate our invention, but are not intended to limit it thereto, the parts indicated bein by weight g '1. 5-chlorisatin-alpha-ch oride having the P b b -formula; .1

' prepared in the usual manner.from'18,2;parts of 5-chlor'isatin, is'sus ended in 250 cc". of a solution of sodium su fits of strength and slowly heated to 90' C1, while stirring.

The chloride gradually disappears leaving a yellow solution from which any small quantity of dark-colored impure matter is filtered off by suctionr By saturation with sodium chloride the reaction-product may the following formula.

whee boiled with an alkali and subsequently acidified the obtained com' ound is converted into chlorisatin withsplitting off of sulfu'rous acid. If to its aqueous solution a caustic alkaliis added, the solution temporarily assumes a characteristic intense reddish-violet color Unlike the already known 'B-sulfite compound of the chlorisatin, which is split up by. a dilute acid already in the cold, the new compound is fast to dilute acids even in the heat. By concentrated sulfuric acid and hydrochloric acid the compound is decomposed in the heat chiefly with formation of 5-5-dichlorindigo having the probable formula:

In an analogous manner other isatines, for

instance dibromisatin may be transformed Into water-soluble a-derlvat ves.

2. 30 parts'of the sodium salt of the dehydroindigobisulfite corresponding probably to the formula:

OaNa OzNa are suspended in 150 cc. of hot water and then mixed at'90 0., while stirring, with a'concentrated solution of about 10 grams of sodium carbonate. formation of the indigo is complete. The excess of sodium carbonate is thenremoved by adding a small-quantity of hydrochloric acid and the liquidis separated by filtration from the isolated indigo while hot. By salting out the filtrate with common salt, the sodium salt of the new-isatin derivative crystallizes out in the form of yellow needles. The compound thus obtained is somewhat more readily soluble than the dehydroindigo bisulfite. When treated with an alkali, no

indigo can be recovered therefrom and it shows also in other respects the same typical reactions as the OhlOIlSitfiflderivative pro- I 'duced accordin to Example 1,

3. 30 arts 0 the sodium salt of the tetra bromode ydroindigo bisulfite corresponding probably to the formula:

S0;Na SOaNa rsee Kalb Berichte der deutschem chem. esellschaft vol. 42, page 3661) are dissolved in 200 cc. of hot Water and, after addition of 10 grams of sodium sulfite warmed on the water-bath for 2-3 hours. The tetrabrom indigo is then filtered off by suction and the Stirring is continued .until the sodium salt of the dibromisatin derivative is isolated by salting it out with common-salt. This sodium salt is readily'soluble in hot Water and crystallizes out on cooling in the form of coarse needles. The compound so obtained shows the same characteristic properties as the chlorisatin derivative described in Examplev 1. It can be. converted into dibromisatin by a careful treatment with an alkali .and subsequent acidification.v It is identical with the dibromisatin' derivative obtainable by subjecting dibromisatin chloride to reaction with a sulfite according to Example 1.

We claim:

1. As new products, the sulfite-derivatives of an isatin, containing in the molecule two sulfurous acid residues; being fast to dilute coloration without there being any formation of indigo corresponding probably to the general formula:

R /80aNa I soiNa wherein B may be substituted.

2. As a new process, the preparation ofa water-soluble isatin-alpha-derivative, which consists in causing a sulfite to act upon an isatin-alpha-chloride.

3. The process of preparing a water-soluble isatin-alpha-derlvative, which consists in causin sodium sulfite to act upon an isatin-alp a chloride.

4. As a new product the compound of the probable formula fluorescence.

5. The process which comprises suspending an.isatin-alpha-chloride in an aqueous solution of sodium sulfite of about 10% strength and heating the solution While stir- MAXIMILIAN P. SCHMIDT. OTTO HERRMANN. 

